Energy harvesting to build a Carbon Monoxide Detector with no battery


There are a few devices that work tirelessly to protect our lives. We’re talking about smoke detectors and carbon monoxide detectors. Increasingly these either need to be hardwired into the home, or have a sealed battery which is good for ten years (in the case of smoke detectors). [Gelmi] recently had to change the battery in his Carbon Monoxide detector — which happens very rarely — and he it got him to thinking. If the batteries need to be changed so rarely, how hard would it be to harvest energy to power the device?

Our first thought was that he’d use inductance like those spy birds which perch on power lines. But instead he went for the heat lost from using the hot water spigot. Above you can see his test rig which attached a Peltier device to the faucet in his bathroom. Whenever you turn on the hot water the faucet also heats up. The differential between faucet temperature and ambient room temperature generates a small amount of power. This is a suitable source, but only if he could also cut the amount of power needed by the detector. This adventure takes him down the rabbit hole, learning about how the sensors work and designing for reliability at the lowest consumption level possible.

The faucet application might seem peculiar. But if you use a natural gas water heater you want a carbon monoxide detector near it. Attach the Peltier to the outflow and every time any hot water tap in the house is opened your system will get a bit of a recharge.

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Generating electricity from alcohol


Here’s a thermoelectric generator which [x2Jiggy] built. The concept uses heat from a flame, biased against cooler temperatures produced by that huge heat sink making up the top portion of the build to produce electricity via the Peltier effect.

The build is passively cooled, using a sync assembly that takes advantage of heat pipes to help increase the heat dissipation. A nearly flat heat sink makes up the mounting surface for the hot side, which faces down toward a flame driving the generator. [x2Jiggy] started the project by using a can, wick, and olive oil as the heat source. He managed to get about 2V out of the system with this method. What you see here is the second version. It swaps out the olive oil lamp for an alcohol stove. The cans with holes punched in them act as a wind screen while also providing a stable base. This rendition produces about 3V, but it doesn’t sound like there are any precise measurements of what it can do under load.

Temperature controlled wine cellar substitute


Serious wine enthusiasts keep their bottles in a room built for the task. If you don’t have that kind of space you can still fabricate a similar storage environment. This foam box keeps stored wine at a controlled temperature. It also keeps light off of the precious goods. [Michael] built it himself to use in his apartment and published a description of the build process.

He picked up some foil-coated foam board from the home store. Six sections come together into a box about the size of a mini-fridge; 24″ by 24″. A square hole was cut in the center of the top section. This receives the smaller of two heat sinks mounted to a Peltier cooler. The temperature inside is monitored by a thermistor which [Michael] tore out of an old iPod battery. To give him some visual feedback on the internal temperature he added that yellow and black striped meat thermometer.

Since this is for long-term storage, we’d bet the system is rather efficient. As long as the door isn’t frequently opened the temperature change should be quite slow thanks to the insulation and the cool liquid in wine bottles.

LTC3105 and LTC3109 energy harvesting chips


[Shahriar] devoted the lastest episode of The Signal Path to looking at energy harvesting chips. These parts are designed to gather energy from non-traditional sources as efficiently as possible. The full episode, which is embedded after the break, is about one hour long. It starts with a bit of background about the nature of these parts, and a brief overview of the wide-range of chips available. Each is suited for a different type of energy source.

He moves on to test and explain the LTC3105 and the LTC3109. The former is shown above on a development board. [Shahriar] hooks it up to his bench equipment to compare its performance to the published specs. This culminates in a circuit that uses a solar cell as the source with a super capacitor used as storage. The latter is connected to a Peltier cooler and used to convert the potential energy of ice cubes to electrical energy which charges his iPhone for about thirty seconds. This might be useful in that Peltier generator we saw last week.

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An actively cooled cloud chamber

This cloud chamber is designed to keep the environment friendly for observing ionizing radiation. The group over at the LVL1 Hackerspace put it together and posted everything you need to know to try it out for yourself.

A cloud chamber uses a layer of alcohol vapor as a visual indicator of ionizing particles. As the name suggests, this vapor looks much like a cloud and the particles rip though it like tiny bullets. You can’t see the particles, but the turbulence they cause in the vapor is quite visible. Check out the .GIF example linked at the very bottom of their writeup.

The chamber itself uses a Peltier cooler and a CPU heat sink. The mounting and insulation system is brilliant and we think it’s the most reliable way we’ve seen of putting one of these together. Just remember that you need a radioactive source inside the chamber or you’ll be waiting a long time to see any particles. They’re using a test source here, but we saw a cloud chamber at our own local Hackerspace that used thoriated tungsten welding rods which are slightly radioactive.

[Thanks JAC_101]

Scavenging from consumer electronics to make a flame-powered phone charger

[Gigafide] just finished building this flame-powered phone charger. The concept is not new. He grabbed a Peltier cooler and used the temperature differential between a flame and a heat sink to produce electricity used by the charger. If you search around here enough you’ll find plenty of candle-powered devices, and a few hacks that use a Peltier device in a bit more interesting way. But we really like his high-production value video, straightforward explanation of the concepts, and ability to source the components in consumer devices. We don’t think you’ll be disappointed by his video found after the break.

The Peltier device comes out of a USB drink chiller. It is supported by a metal stand made from electrical box covers and threaded rod. Underneath he’s using a gel fuel can used by the food industry, and above he’s got  CPU heat sink and fan. This setup puts out around 1.5V but he’ll need a boost converter to charge a phone with that. A single AA battery charger meant to power your phone in a pinch is perfect for this application.

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Check it out, my clothes are electric. No, seriously

Someday you may be able to use your crotch or armpits to recharge that cellphone. Heck, maybe there won’t even be a battery, just a capacitor which gets its juice from Power Felt, a fabric that converts body heat to electricity.

Now we mention the nether-regions because it’s funny, but also because it makes the most sense. Researchers have developed a fabric containing carbon nanotubes used in a way that generates electricity based on a temperature differential. We figure the areas on the body that have high heat loss would be the most efficient locations for the fabric since it is currently extremely expensive to produce (the hope is that mass-production would reduce cost by orders of magnitude). So we think battery-charging briefs are a definite possibility.

What we see here is a nano-scale Peltier electricity generator. It’s the same concept as this candle-based generator, except the increased efficiency of the Power Felt lets your wasted body heat take the place of the flame.

There’s a white paper on the topic but you can’t get at it without surrendering some [George Washingtons].

[via Reddit and Megadgets]